In a satellite communication system, a network of satellites provides telecommunications services to terrestrial-based subscribers. In such a system, the satellites maintain communications with terrestrial-based gateways so that control and subscriber information can be exchanged. These gateways also provide an interface with terrestrial wireline switched telephone networks. Typically, the links that the satellites maintain with the terrestrial-based gateways are of a substantially high bandwidth. Therefore, the terrestrial-based gateways use high frequency microwave or millimeter wave frequencies in order to maintain the high bandwidth communications link with the orbiting satellite.
In a typical terrestrial-based gateway, a traveling wave tube is used to uplink the information to the satellite. A traveling wave tube can be selected for use in a terrestrial-based gateway due to its capability to provide high power signals. However, there are several disadvantages in using a traveling wave tube in a terrestrial-based gateway. One disadvantage of a traveling wave tube is relatively poor signal to noise performance. A second disadvantage of a traveling wave tube is that their use can often be cost prohibitive due to the inherent complexity and size. Other disadvantages of the use of a traveling wave tube is their comparatively low reliability, as well as the requirement for a large high voltage power supply required for tube amplifiers. These high voltage power supplies present safety issues for personnel who would repair the traveling wave tube, or who otherwise have a need to be in close contact with the traveling wave tube amplifier.
In a satellite communications system, it is also frequently desirable to provide different classes of service in the terrestrial-based gateway. Typically, these classes require power levels of between 10 and 100 watts of output power in accordance with the transmit data rates used in the gateway to satellite uplink. Therefore, in designing a network of terrestrial-based gateways, it is necessary to employ traveling wave tubes of varying size in order to provide the various output power levels.
In previous designs which make use of solid-state amplifiers having power outputs which are coupled to waveguide combiners, broad wall waveguide coupling is used. Additionally, the waveguiding structures incorporate no special means for increasing combining efficiency. Further, the designs are not optimized for low cost, high volume manufacturing environments.
Therefore, what is needed, is a low cost, high power, reliable solidstate high frequency amplifier for use as a traveling wave tube replacement. What is also needed, is a modular based high frequency power amplifier which can be used to support varying power output levels which can be used to provide classes of service in the terrestrial-based gateway.